CN101146641A - Method for preparing medical stent - Google Patents

Abstract

The invention relates to a method for preparing stents, with a stent blank subjected to a work process, in which the desired pattern is cut through the stent blank by evaporating the stent material with a diode-pumped fibre laser. The used fibre laser is preferably a picosecond laser having a minimum power of 20 W and a repetition frequency above 1 MHz.

Description

Method for preparing medical stent

field of invention

The present invention relates to a method for the preparation of medical stents by diode-pumped fiber laser technology. The methods of the invention can make scaffolds from metals, plastics, and biopolymers, among other materials.

state of the art

bracket

A "stent" is a device inserted at a blockage in a blood vessel or any other tubular structure to keep the passageway open. Stents are common in medical use in the treatment of various vessel or catheter blockages. Stents are small tubular meshes that are installed in the expanded state within the vessel to be treated, for example after balloon angioplasty or mechanical plaque removal. The stent has the function of keeping the treated vessel site open.

Stents can be classified according to the material used, the structure, the mode of installation and the surgical purpose of application, and according to the temporary or permanent purpose of use.

Coronary stents (referred to herein as stents) are stents that are installed in coronary arteries and may be self-expanding, balloon expandable or thermal memory stents. The material used in the stent can be made of stainless steel, Nitinol, polymer-coated stainless steel, drug-coated stainless steel, biopolymer, coated polymer, memory metal or any other coated or Composition of uncoated material.

Stents typically have a wall thickness approximately in the range of 0.1 mm to 0.15 mm and their length typically in the range of 15 mm to 30 mm. Depending on the purpose of use, the stent has a typical diameter in the range of 0.8 to 2 mm or more, depending on the purpose of use.

US patent application 2004/0024485 A1 discloses the use of lasers in the manufacture of stents, which are manufactured in pressurized oxygen. This is said to increase the burning effect of the laser beam. The use of water for cooling purposes is also stated.

US Patent Specification 6 696 667 B1 states that the laser beam focus can be avoided by using planar scanning to move the laser beam focus on the x-axis (longitudinal) of the stent blank so quickly that no material plasma has time or can form. thermal damage caused by beams. Said reference also describes known laser applications such as Nd:YAG, EXCIMER, copper vapor lasers, tube or diode pumped lasers and femtosecond lasers.

Femtosecond lasers typically have a pulse length of 150-300 femtoseconds. This naturally does not cause severe thermal damage, however, femtosecond lasers have the disadvantage of slow machining processes.

US patent specification 6 696 667 B1 discloses a total pulse length of 100 μs (microseconds) when using a Q-Switch-Nd:YAG: laser. This device is currently the most frequently used laser in stent manufacturing.

The same reference thus states that stent cutting is based specifically on combustion and that no plasma is generated since it damages the stent.

US patent application 6 369 355 discloses a method of manufacturing a stent by means of a laser, which method is based on patterning in the stent material. This pattern formation is clearly based on combustion, ie melting. The reference states that the laser beam focal point can be reduced from 1.06 μ (micrometer) to about half, more specifically to 0.532 μm (μ). The laser used was a Q-switched Nd:YAG laser with a laser pulse length below 100 ns (nanosecond). The pulse repetition frequency is shown to be up to 40KHz.

According to this reference, the reduction of the focal point of the laser beam is said to reduce deformation of the metal portion of the stent. According to said reference, carbon dioxide (CO ₂ ) or oxygen is injected towards the laser beam machining site via a separate nozzle connected to the laser.

Laser cutting based on combustion, ie melting, of a stent blank always involves heat transfer to the rest of the stent material. It will not work with any cooling method as this will interfere with the actual operation i.e. stent cutting.

In addition, it is known to use a combination of stent rotational movement and longitudinal reciprocating movement (CNC) during laser cutting.

In addition, all current stent manufacturing methods require the following working steps: a) ultrasonic cleaning of the stent, b) dissolution in TKL for more than 8 minutes, c) electrochemical polishing, d) repeated ultrasonic cleaning, e) sterilization by said method and f) metal tempering with preheating at temperatures in the range +900-1000°C.

Summary of the invention

The purpose for which the stent is used requires very high precision manufacturing methods. Thus, current methods are very expensive, complicated and slow. Despite continuous developments in manufacturing methods, current stents are still not of good quality.

The first problem with the manufacturing method arises from the process used to cut the metal stent. Using a laser is the most common way of cutting stents, no other thermal method is applicable due to the small size of the workpiece. This is why the type of laser is a key issue in the choice of fabrication method.

A typical stent pattern is illustrated in Figures 7a and b, while Figure 8 shows a prior art cutting device and process. A first problem arises during the cutting of such patterns. When using conventional laser technology, a major part of the energy consumed in the process is conducted to the machined workpiece in the form of thermal heat, causing multiple deformations of the scaffold material, which subsequently affect the scaffold and the material used therein nature.

Such an effect is the fragility and broken atomic structure of the material being processed. To avoid such effects, the finished scaffolds were preheated at +950°C. The preheating process has a duration of about four hours.

If the metal pipe is sound, preheating usually has a beneficial effect. However, after laser cutting by the stent blank wall, said wall has a thickness of only about 0.1 mm.

The laser beams used in prior art lasers have long pulses and high energy, in other words the actual process takes place by combustion, ie melting the metal where the laser beam penetrates through the material.

The temperature is then 2000-6000° C. in the region affected by the laser beam, and a major part of the laser beam energy is delivered into the scaffold material. Such a thermal blockage has a very detrimental effect on the quality of the base carrier blank material.

The most frequently used laser type is the Nd:YAG laser. At that time the pulse length was on the order of microseconds and the repetition rate was in the range of 50 to 2000 Hz. The lasers are crystal lasers, which can be tube or diode pumped. The laser pulses are thus long, thus generating thermal shocks in the metal, resulting in poorer metal quality of the stent.

When using this technique, very sharp edges are formed at the cutting location and the cutting path will be indeterminate due to the molten metal. In addition, loose portions remain adhered to the stent during cutting, and it should be necessary to remove such portions before the stent is delivered to its intended use.

Thus, there have been attempts to solve the problem by subjecting the scaffold to an electrocatalytic polishing process. However, the results of this processing step are not reliable.

A third problem lies in the fact that the raw material used as the bracket blank tube hardens during the manufacturing process and when the hard metal is subjected to localized thermal shocks, the metal quality is greatly weakened and considerable of stress.

After the above process, the laser-machined and electrocatalytically polished support was placed in a tempering furnace, where the temperature was raised to about +950°C. The preheating process has a duration of approximately 4 hours. There would still remain considerable stresses in the support, and it could no longer be fired into a straight shape, but also had an irregular surface structure.

6 and 8 illustrate a prior art stent manufacturing method and cutting device.

The known method is illustrated in FIGS. 6 and 8 . Figures 7a and 7b illustrate typical stents.

The present invention has now been found to solve the above-mentioned problems.

The present invention relates to a method of manufacturing a stent wherein a stent material is laser machined such that the stent blank is subjected to a process where a desired pattern is cut through the stent blank by evaporating the stent material with a diode pumped fiber laser.

The invention which has now been found is based on the unexpected observation that diode-pumped pulsed lasers, especially high-efficiency lasers of at least 20 W picoseconds, are suitable for the manufacture of high-quality stents. The production is considerably faster than the above-mentioned method, and several processing steps required in the above-mentioned method can be completely omitted. In this way, stent manufacturing is significantly more affordable than before.

Since the stent can now be manufactured in a vertical position, unlike the above method, it will not be subject to the same forces caused by gravity which tend to bend the stent as the prior art methods.

The invention also offers the possibility to integrate sterilization, quality control and packaging steps in a closed production process. This facilitates a high-quality and reliable overall process fully adapted to the purpose of the stent use.

Attached picture

Figure 1. Stent manufacturing device according to the invention, wherein the working space is a sealed vacuum chamber (1 ), for example made of metal.

Figure 2. Station (15) for machining stent blanks (19).

Figure 3. Diagram of the operation of the setting unit (7).

Figure 4. Operational top view of the fixing unit (7).

Figure 5. Schematic scheme of scaffold fabrication method.

Figure 6. Schematic scheme of the prior art stent manufacturing method.

Figure 7a. Typical scaffold pattern.

Figure 7b. Typical scaffold pattern.

Figure 8. Prior art stent cutting device and machining method.

Detailed description of the invention

The present invention relates to a method of manufacturing a stent wherein a stent material is laser machined such that the stent blank is subjected to a process wherein a desired pattern is cut through the stent blank by evaporating the stent material with a diode pumped fiber laser.

In one embodiment of the invention, the power of the diode pumped fiber laser is at least 20W, preferably at least 50W and most advantageously at least 100W. Such a diode pump laser is a picosecond or femtosecond laser, preferably a picosecond laser.

The picosecond lasers are preferably modularly enhanced and distributed fiber-enhanced picosecond lasers. Such a diode-pumped picosecond fiber laser also uses pulse frequencies above 1 MHz, preferably above 10 MHz and most advantageously above 40 MHz.

With a module-enhanced distributed pulsed laser approach, it is possible to achieve, for example, 1000 W of net laser power, which can be distributed over ten rack fabrication modules without increasing the price of the laser. The laser beam can be directed through an optical fiber and via an optically corrected scanner to the working position.

In a particularly advantageous embodiment of the invention, the stent is cut with a 100 W picosecond laser with a pulse length of approximately 20-30 ps, a repetition rate of approximately 20 MHz and an individual pulse power of approximately 5 μJ.

Depending on the material, the pulse power is approximately 1-15 J/cm ² in the method of the invention.

In one embodiment of the invention, the stent blank is made of a metal or a metal compound. In this case, the stent blank is preferably preheated to a soft state before the pattern is cut through the stent blank with a diode pumped fiber laser.

In a second preferred embodiment of the invention, said stent blank is made of a polymer, biopolymer or ceramic material. The stent blank can also be made of other materials. The stent blank does not have to consist of a single material. Stent blanks made of the aforementioned materials can also be coated with metals, metal compounds, polymers (plastic) or biopolymers. Additionally, the finished stent can be coated with a drug product.

In the method of the present invention, an optically corrected planar scanner is preferably used to direct the laser beam to the workpiece, ie the stent blank. The actual process is preferably carried out on a vertically positioned workpiece.

In a preferred embodiment of the invention, an automated stent blank reserve is used. All processes in the manufacture of the stent are preferably automated and they include all necessary processes, including packaging.

The method of the present invention preferably uses a sealed vacuum chamber as a workspace, where the process can take place under gaseous atmosphere, vacuum, pressurization, or a combination or combination of these.

Particularly advantageous results are achieved if the entire process is carried out in a vacuum and/or under a gas atmosphere, since this allows the entire process to be carried out continuously or in separate work steps as required.

In a preferred embodiment of the invention, the stent blank is fully machined over its entire length, and only then is it cut to its final length.

In the method of the invention, the stent blank is transferred to the working chamber, preferably in a warm and sterile state. An advantageous way of delivering the stent blanks to the workshop is to deliver them in special cassettes. This allows up to hundreds of stent blanks to be loaded into the device at one time.

In a further preferred embodiment of the present invention, the scaffold quality control, packaging and code affixing are carried out automatically in a closed and sterile space. Such a space may contain vacuum, gas, ultraviolet light and heat, or a combination of these.

The method of the invention should not be limited to stents only, as it is applicable to the cutting of other medical implants, such as screws made of biopolymers or metals.

Thus, the method of the present invention differs from known methods by the fact that the raw material is a preheated full-length stent blank and has a final softness from which a real stent is formed. If deemed necessary, the stent blank can be pre-polished both internally and externally, using eg electro-catalytic methods. A polished tube with a length of 200-300mm is considerably easier and more economical than a polished discretely machined stent with a length of 15-25mm.

According to said new method, it is essential that, in the preheated state, i.e. soft, the stent blank can be machined without causing problems like those related to the prior art methods: thermal shock, deformation of the stent material, burrs, rough surfaces wait.

This is therefore possible on the following conditions: the fiber-enhanced laser is a) diode-pumped, b) has a high frequency 1-100 MHz, c) is a picosecond laser, and its d) pulse power is sufficient, such as 1 -15 J/cm ² (joules/square centimeter). All energy directed to the stent blank will be dissipated only by evaporation of the material to be removed in the cut groove. In this case, the remaining stent material will not experience any kind of thermal effect, the properties of the preheated soft metal will not change, and the cut line will be clean on the surface without burrs or any other effects. Since, unlike the methods described above, it is currently possible to manufacture the stent in a vertical position, it will not experience forces caused by gravity and will not tend to bend the stent like those that occur in prior art methods.

Microlinears, i.e. robots, carry out the entire process quite automatically based on the provided documentation, and on top of this, packaging and sterilization have now been integrated in automated manufacturing methods. In addition, the finished stent can now be packaged under a gas atmosphere, in which the protective gas remains after sealing, thus naturally ensuring complete sterility over a very long period. The package may also contain indicators indicating the function of the protective gas, in other words that the stent is free from bacterial or viral infection.

The invention that has now been found thus facilitates the manufacture of high quality stents at significantly lower cost than before, while excluding such stent treatment steps previously required in the manufacturing process. The speed of stent manufacturing will be significantly accelerated, and the potential integration of sterilization, quality control and packaging steps in a closed production process allows a high quality and safe overall process, well suited for the purpose of use of the stent.

Example

The method of the invention for the manufacture of the stent is described below, without however limiting the invention to the examples given here.

Example 1

This example describes a method for manufacturing a stent according to the invention, wherein the working space is a sealed vacuum chamber ( 1 ), for example made of metal, and which can have any shape, FIG. 1 . The round box and the round receiver will result in a more favorable design if the bracket blank box (2) has been placed in the chamber.

The support box (2) can move freely in the peripheral direction of the chamber (1). It preferably has a linear or stepper motor. This makes it possible to control the movement of the box (2), thus mounting the bracket blanks (3) inside the box (2) in the proper position from where the transfer and fixation unit (7) can retract (8) them.

When the unit (7) that transfers and fixes the stent blank has clamped the stent blank (3), it engages it in a "vertical position" in the hole (10) of the actual stent machining station (8). The stent fixing unit (11) is dedicated to fixing the stent blank at the correct height in the stent machining station (9) so that the laser beam (4) reaches the stent blank through the optically corrected scanner (6), which engages Machining table (9). When the rack is complete, a microrobot/manipulator (12) grips the finished rack and moves it to an intermediate storage (14), which can also be an automatic packing station if the chamber (1) is filled with protective gas. The automatic packaging station may also contain quality control, whose function is carried out by a fully automatic unit equipped with a digital camera and capable of identifying even the smallest defects.

Example 2

This embodiment describes a table (15) for machining a stent blank (19), which is placed in the center (18) of the table, with movable stent fasteners around it ( The central axis of 17) rotates (20) and said fastener (17) receives its motion from a linear or stepper motor (16). The machining station is illustrated in FIG. 2 .

According to the invention, a stent blank (19) is machined with a fiber-enhanced diode-pumped picosecond laser, from where the beam is directed through an optical fiber to an optically corrected (24) scanner (26), allowing the entire stent length (25) Machining is performed as a finished stent (28), simply by rotating (20) the stent blank (19) about its own axis. Such a track is very easy to control with a precision of ±µm. According to the present invention, there is no longer a need to be concerned with vertical motion since this is maintained with multiple optically corrected planar scanners (24) and (26). When the stent (23) is complete, the vertical linear (21) grips the stent blank (19) and moves it (19) (27) to the desired height (28), holding the support through the stent blank if required Support blank (19) on the axle (22) of (19).

The stent blank (19) is only moved around its own central axis by approximately 0.5° per step pulse. With a net laser power of 100W, there will be about 36 pulses per second, and during a total machining time of about 36 seconds, the movement is usually sufficient for the stent blank without shifting its position.

As the entire process is carried out in a closed space without cooling gas of any kind, there is no air flow affecting the workpiece or precision during the cutting process. The picosecond laser used in the method of the invention also does not have any thermal effect on the stent blank in said method. Thus there will be no stress in the scaffold material. This is why the stent blank has to be supported at its free end.

The above issues should be emphasized as it should be understood why the prior art references describe the support of the stent/stent blank during the process.

The bracket blank (19) and especially the machined area of the bracket (23) also require strong support in currently known laser applications because, first of all, the fast x-axis movement and the reciprocating y-motion Physical location has a substantial impact. Second, precisely, the thermal shock generated by the laser and the stresses generated in the stent tend to alter the laser focus considerably, thus resulting in inaccurate cutting. The use of an air flow that enhances or cools the laser beam, as disclosed in prior art references, will have a substantial effect on the positional stability of the stent. This of course has very detrimental effects on laser operation, since the laser beam focus will not be correct either. Therefore, the method described here can solve all these problems.

The scaffold fabrication module shown in Figure 2 is located in a sealed controlled space, such as a vacuum chamber. The generation of the pattern (1) and the stent pattern produced by the laser in the stent blank (19) does not generate heat, even though the temperature of the material plasma is typically about +1,000,000°K. This is due to the fact that the heat is all bound to the atoms removed from the support (23) by evaporation and subsequently removed from the chamber by vacuum venting, usually evacuation.

In front of the planar scanner (26) corrected by the optics (24), preferably also place a) a negatively charged electric field, so that the volatile atoms do not pass in that direction, and/or b) an optical A box of plastic film that progressively advances as it is wound. This is a solution to the problem of keeping the optically constant cleanliness of the laser device without the constraints of directing the laser beam to the stent area (25).

Example 3

This embodiment is a more detailed description delivered in FIG. 1 , ie the operation of the fixation unit ( 7 ), FIG. 3 . Said fixing unit is in a controlled state, inside a vacuum chamber (29), for example, where a bracket box (30) is provided to a vertically positioned bracket blank (31), which rotates around eg its own central axis, the bracket blank ( 31 ) against eg the bottom ( 40 ) of the stand box ( 30 ). Each time, the bracket box (30) advances another bracket blank (31) to the transfer and fixation area, where an engaging mechanism (32) is provided for clamping said bracket with its jaws (39). Place the jaws (39) in the motorized (33) central body (35) capable of moving the stent blank in all dimensions (34) in the plane (36) touching the line (37), moving the The bracket blank is guided (38) to the machining station.

Example 4

This example describes the operation of the stationary unit viewed from above, FIG. 4 . The circular stent blank (41) is preferably kept slightly inclined in the stent box. According to the invention, the stent fixation unit and the transfer means are preferably able to perform any trajectory (43, 47 and 49) in fully three-dimensional parameters.

According to the illustrated principle of operation, the jaws (42) engage the bracket blank (41) by closing (43) against each other, and then the body (46) of the jaw mechanism (42) engages around its own central axis (45 ) is turned eg (47) 180° and moved with a linear conveyor (48) against the stent machining station (49), from where it returns automatically to remove the subsequent stent blank (41).

Example 5

Embodiment 5 describes the technological process of the method of the present invention, FIG. 5 . This method differs substantially from known methods of stent manufacturing and further processing of stents. A significant difference lies in the fact that the stent tube (50) is in "a preheated" form, ie it has its definite softness. The stent tube is also pre-polished.

Therefore, one of the benefits obtained by the method is that no further processing steps are required as in the prior art methods.

While the laser of the new method has undergone an engraving process (51) based on material evaporation at very high temperatures (nearly +1,000,000°K (Kelvin)), it will not be damaged in any way during the manufacturing process. the bracket.

If the package made for the stent is also placed in a sealed workspace under gas atmosphere, Fig. 1(1), then the stent can be placed directly in the package (52) and (54) it can be packaged and ( 55) Seal. In this case, all stent cassettes ( 2 ), along with inserted ( 3 ) stent blanks, are thus sterilized, which are inserted packages, which are located in their own cassettes. The actual chamber ( 1 ) is then also sterilized by a) UV light, b) gas and/or c) heat.

The use of UV light in sterilization is particularly easy because with a chamber Fig. 1(1) made of stainless steel, UV light will be reflected everywhere. The combination of UV light and protective gas will result in a 100% sterile space.

A second application involves the automated sterilization illustrated in Figure 5, where the completed stent is placed in a package (52), placed in a box, for example, and moved to an autoclave filled with protective gas (54) (53), close the lid and finish the product (55).

Example 6

Example 6 illustrates the prior art steps for fabricating a stent, FIG. 6 . In such a method, a pattern is cut through the material wall of the rigid stent tube (50). Burrs, ie irregular cutting marks, are produced during the ongoing process (51). The surface becomes rough and there will be residual burnt metal fragments, burrs and sprays adhering, their removal requiring electro-catalytic polishing of the stent (57). The stent is then passed (58) to a tempering furnace (59), gradually increasing its temperature to approximately +900-+1000°C, and the metal regains its original softness, ie moldability. Since the changeover between processes is performed manually and the racks are exposed to free ambient air, they require, for example, sterilization in step (60), where glass or plastic sealable packages have been placed.

Example 7

Example 7 illustrates a prior art setup for fabricating a stent, FIG. 8 . Such a stent making machine (63) is generally equipped with two electric motors, eg linear and stepper motors, allowing the necessary high precision work movements (68) and (69) to be performed. These movements consist of reciprocating paths (68) and rotational movements (69), which have been programmed synchronously so that the angle of incidence of the laser beam (66) at the desired location is as precise as possible.

The above describes the use of an optically corrected scanner (70) and thus this is an improvement since no reciprocating linear motion (68) is required so that in theory this should lead to a more regular cutting trajectory, however does not imply a higher stand quality.

The use of a Nd:YAG laser was described above, causing the above problems, with further processing in horizontal position (73) and fabrication in open space (65). Likewise, the stand (67) is lowered (71) into the universal receptacle (72).

In prior art stent manufacturing methods, the stent device ( 63 ) is kept in a constant horizontal position, as shown by the stent blank ( 64 ), FIG. 8 . This means that the laser process (68), the spot beam which requires longitudinal reciprocation (68) of the stent blank (64) and the scanner which performs the process over the entire length of the stent (67), is performed horizontally. For work performed in a horizontal position, the support will be the most unstable because the workpiece, the support (57) tends to move downwards under the earth's gravity (65) and because movement (68), and because of stresses in the bracket due to processes (60) and (70). This is why prior art methods use a different form of support system threaded into the stent because otherwise it would be very difficult to do the laser cutting methods (66) and (70).

Subsequent processing steps consist of separating the scaffold (67) from the scaffold blank (64), said scaffold falling freely (71) into a box where said scaffold (72) is mixed.

This is followed by the processing steps illustrated in Figure 6, all of which require manual operations because it is difficult to automate a process that was not originally designed as such.

Claims (14)

1. method of making support, wherein timbering material is processed by laser engine, it is characterized in that described support blank is carried out technical process, wherein make required pattern-cut pass described support blank by optical fiber laser evaporation timbering material with diode pumping.

2. the method as limiting in the claim 1 is characterized in that it is 20W that described diode-pumped laser has minimum power, preferred minimum power be 50W and the most advantageously minimum power be 100W.

3. the method as limiting in claim 1 or 2 is characterized in that described diode pumping optical fiber laser is psec or femto-second laser, preferred picosecond laser.

4. the method as limiting among the claim 1-3 is characterized in that picosecond laser is the picosecond laser that strengthens with distributed optical fiber that module strengthens.

5. the method as limiting among the claim 2-4, it is characterized in that by the pulse that diode pumping psec optical fiber laser adopts have more than the 1MHz, the repetition rate more than the 40MHz more than the preferred 10MHz and the most advantageously.

6. the method as limiting in the claim 1 is characterized in that described support blank made by metal or metallic compound.

7. the method as limiting in the claim 6 is characterized in that with the diode pumping optical fiber laser described pattern-cut being passed before the described support blank, and described support blank is preheated to soft condition.

8. the method as limiting in the claim 1 is characterized in that described support blank is to be made by polymer, biopolymer or ceramic material.

9. as the method for qualification in the claim 1, it is characterized in that the plane scanner of described method use optical correction, utilizing this plane scanner that laser beam is directed to work piece is on the support blank.

10. the method as limiting in the claim 1 is characterized in that carrying out described technical process with the work piece in the upright position.

11., it is characterized in that described method use automatic supporter blank deposit as the method that limits in the claim 1.

12. as the method that limits in the claim 1, it is characterized in that whole technical process are automatically and comprise the technical process of whole necessity, described technical process comprises packing.

13. as the method that limits in the claim 1, it is characterized in that described working space is the vacuum chamber of sealing, there in gas atmosphere, vacuum, pressure or these combination or unite under the use described process can take place.

14. as the method that limits in the claim 1, it is characterized in that can be on its whole length the described support blank of machining, and just after this, be cut into its suitable length.

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